New CT scans of the spiral-tooth fossil, Helicoprion, resolve a longstanding mystery concerning the form and phylogeny of this ancient cartilaginous fish. We present the first three-dimensional images that show the tooth whorl occupying the entire mandibular arch, and which is supported along the midline of the lower jaw. Several characters of the upper jaw show that it articulated with the neurocranium in two places and that the hyomandibula was not part of the jaw suspension. These features identify Helicoprion as a member of the stem holocephalan group Euchondrocephali. Our reconstruction illustrates novel adaptations, such as lateral cartilage to buttress the tooth whorl, which accommodated the unusual trait of continuous addition and retention of teeth in a predatory chondrichthyan. Helicoprion exemplifies the climax of stem holocephalan diversification and body size in Late Palaeozoic seas, a role dominated today by sharks and rays.

An extraordinary find allowing scientists to see through the head of the 'fuxianhuiid' arthropod has revealed one of the earliest evolutionary examples of limbs used for feeding, along with the oldest nervous system to stretch beyond the head in fossil record.

Until now, all fossils found of this extremely early soft-bodied animal featured heads covered by a wide shell or 'carapace', obscuring underlying contents from detailed study.

But a new fossil-rich site in South China has been found to contain arthropod examples where the carapace has literally been 'flipped' over before fossilisation – allowing scientists to examine the fuxianhuiid head to an unprecedented extent.

The study, published today in Nature, highlights the discovery of previously controversial limbs under the head, used to shovel sediment into the mouth as the fuxianhuiid crawled across the seabed, millions of years before creatures emerged from the oceans.

Scientists say that this could be the earliest and simplest example of manipulative limbs used for feeding purposes, hinting at the adaptive ability that made arthropods so successful and abundant – evolving into the insects, spiders and crustaceans we know today.

Using a feeding technique scientist's call 'detritus sweep-feeding', fuxianhuiids developed the limbs to push seafloor sediment into the mouth in order to filter it for organic matter – such as traces of decomposed seaweed – which constituted the creatures' food.

Fossils also revealed the oldest nervous system on record that is 'post-cephalic' – or beyond the head – consisting of only a single stark string in what was a very basic form of early life compared to today.

"Since biologists rely heavily on organisation of head appendages to classify arthropod groups, such as insects and spiders, our study provides a crucial reference point for reconstructing the evolutionary history and relationships of the most diverse and abundant animals on Earth," said Javier Ortega-Hernández, from Cambridge's Department of Earth Sciences, who produced the research with Dr Nicholas Butterfield and colleagues from Yunnan University in Kunming, South China. "This is as early as we can currently see into arthropod limb development."

Fuxianhuiids existed around 520 million years ago, roughly 50 million years before primordial land animals crawled from the sea, and would have been one of the first examples of complex animal life – likely to have evolved from creatures resembling worms with legs. Arthropods were the first jointed animals, enabling them to crawl.

Fuxianhuiid arthropods would have spent most of their time grazing on the sea floor, using these newly discovered limbs to plow sediment into their mouths. They could probably also use their bodies to swim for short distances, like tadpole shrimps.

The fossils date from the early part of the event known as the 'Cambrian explosion', when life on Earth went from multi-cellular organisms we know very little about to a relatively sudden and wide spread explosion of diverse marine animals - the first recognisable evolutionary step for the animal kingdom we know today.

"These fossils are our best window to see the most primitive state of animals as we know them – including us," said Ortega-Hernández. "Before that there is no clear indication in the fossil record of whether something was an animal or a plant – but we are still filling in the details, of which this is an important one."

While still a mystery, theories about the cause of the 'Cambrian Explosion' include possible correlations with oxygen rises, spikes in oceanic nutrient concentration, and genetic complexity reaching critical mass.

But the new site in South China where these fossils were found could prove to be key in uncovering ever more information about this pivotal period in the history of life on Earth. The Xiaoshiba 'biota' - that is the collection of all organisms preserved in the new locality - in China's Yunnan Province is similar to the world-famous Chengjiang biota, which provided many of the best arthropod fossil records to date.

Chinese fossil forgery in the last decade highlights some troubling trends in Chinese vertebrate paleontology. While fossil forgeries unfailingly stoke public fascination in a field capable of producing the infamous Piltdown man hoax, the widespread damages that forgery causes are often not sufficiently recognized. Amid the renaissance of Chinese paleontology evidenced by stunning discoveries of inconceivable riches of fossils, paleontologic science is treading a path never experienced elsewhere: Commercialization of fossils and all that goes with a quasi-free market of fossil trade that has simultaneously become the boom and bane of Chinese vertebrate paleontology.

A new vertebrate locality from the Lower Permian (Cisuralian) of the Bourbon-l'Archambault basin (Massif Central, France) is reported and its associated flora and fauna preliminarily described. This locality corresponds to a mass mortality assemblage deposited in an aquatic environment. Interestingly, it has yielded hundreds of exceptionally well preserved seymouriamorph specimens, all referred to Discosauriscus austriacus. This exquisite assemblage corresponds to the first seymouriamorph Lagerstätte and the first record of D. austriacus outside the Boskovice basin in Czechia. It enlarges the geographical distribution of the species during the Early Permian, and has new palaeoenvironmental implications regarding the Palaeozoic Bourbon-l'Archambault basin.

A new species of Bolosauridae, Belebey augustodunensis, is described from fragmentary cranial material collected in the late Gzhelian-Asselian beds of the Autun basin, central France. Be. augustodunensis is one of the oldest bolosaurids and represents the first occurrence of the family in France. The dentition of this species is unique within Bolosauridae in exhibiting a progressive shift from a mesio– to a disto-lingual orientation of the tooth apex and lingual facet. Other features show that Be. augustodunensis belongs to the genus Belebey, although it lacks several specializations known in other species of the genus. A review of the valid bolosaurid taxa increases their stratigraphic and geographic distribution, in addition to the description of Be. augustodunensis. The distributions and diversification of Bolosauridae are briefly discussed.

Tuesday, February 26, 2013

Was there ever a YF-24? The US Air Force says no. "Our historians said there is no record of there ever having been a YF-24," says Lt Col Max Despain, an Air Force spokeswoman at the Pentagon. "Perhaps it's being mistaken for an X-24 which wasn't a fighter?"

That said, this old bio for a former test pilot, Colonel Joseph A. Lanni lists such an aircraft--which is curious. So there remains a small possibility a YF-24 might have been squirreled away somewhere out in the desert in Nevada. I say that because Lanni, according to his bio, commanded a classified flight test unit between July 1995 and June 1997.

While the entry in the bio might be a typo, it was certainly not the X-24 that Lanni flew. The Martin Marietta X-24A flew during 1963 to 1975, which was well before Lanni became an Air Force pilot. It's also not likely that Lanni flew the Northrop YF-23 either since he was assigned to Eglin AFB in Florida during the time those jets were flying.

So, what exactly the YF-24 is or was is still kind of a mystery. Your guess is as good as mine.

Intriguing. Not sure I buy it, but the link included in the article is most likely a typo. Still an interesting idea that some group attempted to get something built that was a fighter prototype. It'd also explain why Boeing beat out McDAC for the JSF prototype contract.

Charlie Stross, an author and someone I've been acquainted with online for almost two decades now, links to a paper (PDF) presented at a conference about a theoretical natural nuclear reactor on Mars going boomski. If my math is not too far off, its on the order of 10 times the megatonnage of Chicxulub's impact. Unfortunately, it has a three strikes against it.

The first is that that's enormous and seems unlikely to have possibly reached that concentration of Thorium and Uranium on Mars. That can be confirmed or debunked though. That's the nice thing about science.

The second, also science driven, is that there ought to be a blast crater, even if its a surface kaboomski, its going to be blowing a massive hole. It does not appear to be present. Chicxulub left something after 65+/- million years. Even the Manicouagan Crater is still painfully observable and that is 214+/- million years old. The Vredefort crater is OLDER than the proposed Martian explosion at 2 billion years and still a observable. These are all on a VERY wet, geologically active world

The Laccadive–Chagos Ridge and Southern Mascarene Plateau in the north-central and western Indian Ocean, respectively, are thought to be volcanic chains formed above the Réunion mantle plume1 over the past 65.5 million years2, 3. Here we use U–Pb dating to analyse the ages of zircon xenocrysts found within young lavas on the island of Mauritius, part of the Southern Mascarene Plateau. We find that the zircons are either Palaeoproterozoic (more than 1,971 million years old) or Neoproterozoic (between 660 and 840 million years old). We propose that the zircons were assimilated from ancient fragments of continental lithosphere beneath Mauritius, and were brought to the surface by plume-related lavas. We use gravity data inversion to map crustal thickness and find that Mauritius forms part of a contiguous block of anomalously thick crust that extends in an arc northwards to the Seychelles. Using plate tectonic reconstructions, we show that Mauritius and the adjacent Mascarene Plateau may overlie a Precambrian microcontinent that we call Mauritia. On the basis of reinterpretation of marine geophysical data4, we propose that Mauritia was separated from Madagascar and fragmented into a ribbon-like configuration by a series of mid-ocean ridge jumps during the opening of the Mascarene ocean basin between 83.5 and 61 million years ago. We suggest that the plume-related magmatic deposits have since covered Mauritia and potentially other continental fragments.

A recently discovered comet will make an uncomfortably-close planetary flyby next year — but this time it’s not Earth that’s in the cosmic crosshairs.

According to preliminary orbital prediction models, comet C/2013 A1 will buzz Mars on Oct. 19, 2014. The icy interloper is thought to originate from the Oort Cloud — a hypothetical region surrounding the solar system containing countless billions of cometary nuclei that were outcast from the primordial solar system billions of years ago.

We know that the planets have been hit by comets before (re: the massive Comet Shoemaker–Levy 9 that crashed into Jupiter in 1994) and Mars, in particular, will have been hit by comets in the past. It’s believed Earth’s oceans were created by water delivered by comets — cometary impacts are an inevitable part of living in this cosmic ecosystem.

C/2013 A1 was discovered by ace comet-hunter Robert McNaught at the Siding Spring Observatory in New South Wales, Australia, on Jan. 3. When the discovery was made, astronomers at the Catalina Sky Survey in Arizona looked back over their observations to find “prerecovery” images of the comet dating back to Dec. 8, 2012. These observations placed the orbital trajectory of comet C/2013 A1 through Mars orbit on Oct. 19, 2014.

Could the Red Planet be in for a potentially huge impact next year? Will Mars rovers Curiosity and Opportunity be in danger of becoming scrap metal?

It seems the likelihood of an awesome planetary impact is low — for now.

According to calculations by NASA’s Jet Propulsion Laboratory (JPL), close approach data suggests the comet is most likely to make a close pass of 0.0007 AU (that’s approximately 63,000 miles from the Martian surface). However, there’s one huge caveat.

Due to uncertainties in the observations — the comet has only been observed for 74 days (so far), so it’s difficult for astronomers to forecast the comet’s precise location in 20 months time — comet C/2013 A1 may fly past at a very safe distance of 0.008 AU (650,000 miles). But to the other extreme, its orbital pass could put Mars directly in its path. At time of Mars close approach (or impact), the comet will be barreling along at a breakneck speed of 35 miles per second (126,000 miles per hour).

Also, we don’t yet know how big comet C/2013 A1 is, but comets typically aren’t small. If it did hit, the impact could be a huge, global event. But the comet’s likely location in 2014 is also highly uncertain, so this is by no means a “sure thing” for Mars impact (Curiosity, you can relax, for now).

One thing is looking likely, however. Mars could be in for its own “cometary spectacular.”

Therapsid and other tetrapod fossils from the South African Karoo Supergroup provide the most detailed and best studied terrestrial vertebrate record of the Middle and Late Permian. The resulting biostratigraphic scheme has global applicability. Establishing a temporal framework for these faunas has proven difficult: magnetostratigraphy has been hampered by a Jurassic overprint, and intercorrelation with Permian marine sequences has been equivocal. Here we report U-Pb zircon isotope dilution–thermal ionization mass spectrometry (ID-TIMS) dates for five volcanic ashes interbedded with fossils from the Pristerognathus, Tropidostoma, and Cistecephalus vertebrate biozones of the Beaufort Group. This temporal framework allows correlation to marine zonations and improves understanding of rates of faunal evolution and patterns of basin evolution. Our results identify no correlative vertebrate extinctions in the Karoo Supergroup to the marine end-Guadalupian mass extinction and raise the question of whether there is any record of a terrestrial extinction related to the Emeishan large igneous province.

Friday, February 22, 2013

This week was also brutal though I did move the ball forward on finishing the post, but just could not get it done for today. There are three clades left living in the Xenopermian of anomodonts. They are the descendents of Tiarajudens, the dicynodonts and Venjukoviamorphs (suminids and friends).

Structural coloration underpins communication strategies in many extant insects but its evolution is poorly understood. This stems, in part, from limited data on how color alters during fossilization. We resolve this by using elevated pressures and temperatures to simulate the effects of burial on structurally colored cuticles of modern beetles. Our experiments show that the color generated by multilayer reflectors changes due to alteration of the refractive index and periodicity of the cuticle layers. Three-dimensional photonic crystals are equally resistant to degradation and thus their absence in fossil insects is not a function of limited preservation potential but implies that these color-producing nanostructures evolved recently. Structural colors alter directly to black above a threshold temperature in experiments, identifying burial temperature as the primary control on their preservation in fossils. Color-producing nanostructures can, however, survive in experimentally treated and fossil cuticles that now are black. An extensive cryptic record is thus available in fossil insects to illuminate the evolution of structural color.

A new climate model predicts an increase in snowfall for the Earth's polar regions and highest altitudes, but an overall drop in snowfall for the globe, as carbon dioxide levels rise over the next century.

The decline in snowfall could spell trouble for regions such as the western United States that rely on snowmelt as a source of fresh water.

The projections are the result of a new climate model developed at the National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory (GFDL) and analyzed by scientists at GFDL and Princeton University. The study was published in the Journal of Climate.

The model indicates that the majority of the planet would experience less snowfall as a result of warming due to a doubling of atmospheric carbon dioxide. Observations show that atmospheric carbon dioxide has already increased by 40 percent from values in the mid-19th century, and, given projected trends, could exceed twice those values later this century. In North America, the greatest reductions in snowfall will occur along the northeast coast, in the mountainous west, and in the Pacific Northwest. Coastal regions from Virginia to Maine, as well as coastal Oregon and Washington, will get less than half the amount of snow currently received.

In very cold regions of the globe, however, snowfall will rise because as air warms it can hold more moisture, leading to increased precipitation in the form of snow. The researchers found that regions in and around the Arctic and Antarctica will get more snow than they now receive.

The highest mountain peaks in the northwestern Himalayas, the Andes and the Yukon region will also receive greater amounts of snowfall after carbon dioxide doubles. This finding clashes with other models which predicted declines in snowfall for these high-altitude regions. However, the new model's prediction is consistent with current snowfall observations in these regions.

The key is resolution in the model. I am going to take a look at the paper later assuming I have time and see if the resolution is close to the 1 km range yet. if not, this will only count as a mild improvement over the current models and ought to be taken with a rain of salt as to its real predictive value for precipitation.

Her model, for the continental US, is a neo Oligocene, as I have been calling it.

South Korea's proposed KF-X stealth fighter program has not been short of influential opponents. Now it has another. A defense ministry think tank, the Korea Institute for Defense Analysis, has told a public meeting that the country is not technologically equipped to develop the aircraft, that the project is economically unviable and that the KF-X would not be a successful export product. The institute challenges cost estimates by the Agency for Defense Development, which is leading development of the aircraft.

KF-X development would cost more than 10 trillion won ($9.2 billion), one of the institute's researchers, Lee Juhyeong, has told a seminar on the program. Over the life of the program, the KF-X would cost the country more than twice as much as an imported aircraft, Lee says.

The institute's stance has not previously been publicly stated, although the Naeil newspaper reported last year that it had submitted a confidential report doubting the viability of the project. Now speaking openly, the institute questions whether the U.S. will be willing to help develop the KF-X. Other skeptics wonder how it could be exported in competition with U.S. aircraft, since South Korea would probably have to use major U.S. components, whose export could be blocked by Washington. Another influential think tank, the Korea Development Institute, reported as early as 2007 that the KF-X was not viable.

KF-X program director Lee Daeyearl, of the Agency for Defense Development, told the same seminar that the fighter would cost 6 trillion won in development, 8 trillion in production, and 9 trillion for operations over 30 years, according to an aerospace industry executive who attended.

South Korea needs to develop its own fighters to be capable of upgrading them and to install South Korean weapons systems, Lee Daeyearl says. “It will contribute to the nation's aerospace industry in the future,” Yonhap news agency quotes him as saying. “Without making a first step, we'll have to rely on imported aircraft and that will benefit foreign defense contractors.”

The agency has prepared two series of designs, one for an aircraft with its horizontal stabilizers aft, which it considers to be a U.S. style, and one for a “European” fighter with a canard stabilizer. The aft-tail series has run through the iterations C101, C102 and, now, C103, all with two engines and a single seat. The C102 design was further broken down into three variants: C102E with one engine, C102I with internal weapons and C102T with two seats. Those ideas have been discarded, however; the current aft-tail design is C103. Similarly the C201, C202 (with variants E, I and T) and the current C203 follow the same pattern, except for a canard planform.

The agency proposes that either C103 or C203, whichever was chosen, would then advance through three design standards. Block 1 would be “reduced observable,” which it says would be equivalent to the B-1B, Boeing F/A-18E/F Super Hornet and Eurofighter Typhoon. For its low signature, Block 1 would rely on fuselage and inlet shaping, including edge alignment, and on radar-absorbing material and semi-conformal weapons carriage.

Laminated carbonates of the Rasthof Formation, deposited in the aftermath of the early Cryogenian low-latitude glaciation (Sturtian, 717–662 Ma), preserve abundant round tests of agglutinated microscopic eukaryotes. Previously, fossil tests were reported in two localities (Ongongo and Okaaru) from microbially laminated carbonates in the Rasthof Formation, which revealed a previous unexplored Cryogenian taphonomic window. In order to better understand the lateral variability in these microfossil assemblages, this work systematically examines fossil tests from two additional localities, South Ombepera and Ombepera, and compares their preservation in thinly and thickly laminated microbial laminites. Cap carbonates in South Ombepera and Ombepera contain abundant, hollow, spheroidal agglutinated tests (50 to 225 µm in diameter). Some of these tests exhibit slitlike or triangular apertures. In contrast, much larger, oval tests with a tapering end dominate the assemblages at Okaaru, whereas oval, laterally compressed and round structures with slits, visors, or central apertures are found at Ongongo. The thinly laminated microbial laminites from Ombepera, South Ombepera, and Okaaru also preserve rare agglutinated tubes attributed to fossils of early Foraminifera. At all four localities, the thinly laminated microbial laminites preserve more microfossils than thickly laminated microbial laminites although these two facies commonly interfinger and are interbedded. This difference shows that conditions present during formation of the thinly laminated microbial laminites favored the preservation of round agglutinators, perhaps during early burial, lithification, and fossilization of the test walls.

The Central Tianshan region is a key to evaluate the Paleoproterozoic evolution of the Tarim Block and its correlation with the Columbia supercontinent. In this study, we present U–Pb age data on detrital zircons in Paleoproterozoic schists from Central Tianshan and employ the magmatic age spectra to probe the Precambrian history of the region. We use the U–Pb ages of metamorphic zircons to constrain the Paleoproterozoic collisional event of the Tarim Block, and to evaluate its link with the Columbia supercontinent. The age populations of the detrital igneous zircons and inherited cores show peaks at ∼2544 Ma, ∼2397 Ma, ∼2264 Ma, ∼2161 Ma, ∼1970 Ma and ∼1882 Ma, corresponding to the major tectonomagmatic events previously recorded in the Tarim Block. Combined with the results from previous studies, we conclude that the northern Tarim was an active continental margin from late Neoarchean to late Paleoproterozoic. Zircons in the Paleoproterozoic schists display a wide range of two-stage model ages (3.3–2.7 Ga), revealing prolonged growth of juvenile crust in Tarim from late Paleoarchean to early Neoarchean. The tightly constrained age range of 1830–1788 Ma (weighted mean 1808 Ma) obtained from the metamorphic zircons and overgrowth mantles mark the timing of the thermal event associated with the final collisional orogeny along the northern margin of Tarim, coinciding with the assembly of the Columbia supercontinent.

A new ornithopod dinosaur from Antarctica, Trinisaura santamartaensis n. gen. et n. sp. is diagnosed by a unique combination of characters that includes a scapula with a spike-like acromial process with a strong and sharp lateral crest and longer than other ornithopods, a humerus with a rudimentary deltopectoral crest represented as a thickening on the anterolateral margin of the humerus, and shaft strongly bowed laterally, and an ischium gently curved along its entire length. The holotype specimen comprises vertebral and appendicular elements. The presence of axially elongate distal caudal vertebrae, pubis with long prepubic and postpubic processes, as well as a femur with a distinct anterior trochanter, pendant 4th trochanter and shallow anterior intercondylar groove constitute a combination of characters present in the Late Cretaceous Patagonian Gasparinisaura, Anabisetia and Talenkahuen. The materials were found on the surface enclosed in a hard sandstone concretion collected near the Santa Marta Cove, James Ross Island, from the lower levels of the Snow Hill Island Formation (Campanian). This is the first ornithopod taxon identified from this unit, and the second ornithischian dinosaur, after the ankylosaur Antarctopelta oliveroi. However, other ornithopod reports from nearby localities of James Ross and Vega islands in outcrops of the overlying Lopez de Bertodano Formation suggest that this clade was widely represented in the Campanian and Maastrichtian of the James Ross Basin, Antarctic continent.

Wednesday, February 20, 2013

Paleobiogeography and biodiversity of Late Maastrichtian dinosaurs: how many dinosaur species went extinct at the Cretaceous-Tertiary boundary? Author:

1. Jean Le Loeuff

Affiliations:

a. Musée des Dinosaures, 11260 Espéraza, France

Abstract:

The global Late Maastrichtian non-avian dinosaur apparent biodiversity is extensively surveyed for the first time. It amounts to 104 species (including unnamed forms) in 2010. The real biodiversity being obscured by taphonomical biases and the scarcity of the continental fossil record, a species-area relationship is used to estimate it. The results show that several hundreds (between 628 and 1078) non-avian dinosaur species were alive in the Late Maastrichtian, which is almost an order of magnitude above previous estimates. Because of the complex Late Cretaceous palaeobiogeography, discussions about dinosaur extinction should be based on this estimated real global biodiversity, not on the apparent biodiversity of a single area. Given the mean duration of dinosaur genera (7.7 Ma), the presence of so many dinosaur species in the Latest Cretaceous is consistent with the termination of most lineages at the Cretaceous-Tertiary boundary (the Late Maastrichtian sub-stage is 2.8 m.y. long). The Late Maastrichtian dinosaurian biodiversity is therefore consistent with the sudden extinction of the group following the Chicxulub impact.

a, Photograph of the holotype (Institut Royal des Sciences Naturelles de Belgique, a12818) based on part and counterpart (stitching and focus stacking procedure). b, Detail of the proposed head based on part and counterpart. *, base of hypothetical antenna. c, Detail of legs. d, Same area as in c, inverted grey-scale with some legs colour-coded.

The origin of winged insects (Pterygota), one of the planet’s most diverse lineages of organisms, is assumed to lie in the Devonian, but as an extremely sparse fossil record impedes our understanding of their early diversification, any well-preserved insect fossil from this time would be particularly valuable. Garrouste et al. described an arthropod from Upper Devonian freshwater sediments from the Strud locality in Belgium (~360 million years ago) as an insect, Strudiella devonica. However, based on a thorough re-investigation of the specimen, we conclude that this interpretation is untenable. Hence we believe that, like several other Devonian arthropod remains, Strudiella is not an insect, and utmost diligence should be taken in interpreting poorly preserved Devonian arthropods.

An international team of astronomers has used nearly three years of high precision data from NASA's Kepler spacecraft to make the first observations of a planet outside our solar system that's smaller than Mercury, the smallest planet orbiting our sun.

The planet is about the size of the Earth's moon. It is one of three planets orbiting a star designated Kepler-37 in the Cygnus-Lyra region of the Milky Way.

The findings are published were published online on Feb. 20 by the journal Nature. The lead authors are Thomas Barclay of the NASA Ames Research Center in California and the Bay Area Environmental Research Institute and Jason Rowe of NASA Ames and the SETI Institute in California.

Steve Kawaler, an Iowa State University professor of physics and astronomy, was part of a team of researchers who studied the oscillations of Kepler-37 to determine its size. "That's basically listening to the star by measuring sound waves," Kawaler said. "The bigger the star, the lower the frequency, or 'pitch' of its song."

The team determined Kepler-37's mass is about 80 percent the mass of our sun. That's the lowest mass star astronomers have been able to measure using oscillation data for an ordinary star.

Those measurements also allowed the main research team to more accurately measure the three planets orbiting Kepler-37, including the tiny Kepler-37b.

"Owing to its extremely small size, similar to that of the Earth's moon, and highly irradiated surface, Kepler-37b is very likely a rocky planet with no atmosphere or water, similar to Mercury," the astronomers wrote in a summary of their findings. "The detection of such a small planet shows for the first time that stellar systems host planets much smaller as well as much larger than anything we see in our own Solar System."

Kawaler said the discovery is exciting because of what it says about the Kepler Mission's capabilities to discover new planetary systems around other stars.

Imagine you had a Hubble-class telescope and could use in any way you wanted to explore planets. What would you do with it?

A number of scientists have had the chance to explore that question courtesy of an American spy agency. A year ago, NASA received a surprise phone call from the National Reconnaissance Agency (NRO), which flies spy satellites, asking if it would like two spare, Hubble-class space telescopes. NASA’s managers said,”Yes!,” and now the agency is looking for the best uses for the telescopes. The highest priority is to see if one telescope could be used to meet the needs for the Wide-Field Infrared Survey Telescope (WFIRST) to study dark energy. That potentially leaves a second telescope for other deep space or solar system studies.

Before I describe the concepts discussed at a recent conference, a truth in advertising statement is required. Each telescope represents $250M worth of hardware. However, not all the systems needed for an actual satellite are included, instruments are not included, and the whole lot would need to be launched. Figures I’ve read suggest that turning each telescope into a working observatory would cost approximately $1B, depending on the specifics of the mission. NASA’s current budgets have no room to fund a single mission, much less two. In a few years, there may be room for a mission or two, so the space agency is soliciting ideas.

Too bad you could not lob this sucker to the Jovian system. That'd be beyond awesome for exploring the Galilean Moons. There are two telescopes so you need not worry about choosing only one mission. There are parts for another...if that one could be completed too...

Tuesday, February 19, 2013

Though scientists have long believed that complex organic molecules couldn't survive fossilization, some 350-million-year-old remains of aquatic sea creatures uncovered in Ohio, Indiana, and Iowa have challenged that assumption.

The spindly animals with feathery arms—called crinoids, but better known today by the plant-like name "sea lily"—appear to have been buried alive in storms during the Carboniferous Period, when North America was covered with vast inland seas. Buried quickly and isolated from the water above by layers of fine-grained sediment, their porous skeletons gradually filled with minerals, but some of the pores containing organic molecules were sealed intact.

That's the conclusion of Ohio State University geologists, who extracted the molecules directly from individual crinoid fossils in the laboratory, and determined that different species of crinoid contained different molecules. The results will appear in the March issue of the journal Geology.

William Ausich, professor in the School of Earth Sciences at Ohio State and co-author of the paper, explained why the organic molecules are special.

"There are lots of fragmented biological molecules—we call them biomarkers—scattered in the rock everywhere. They're the remains of ancient plant and animal life, all broken up and mixed together," he said. "But this is the oldest example where anyone has found biomarkers inside a particular complete fossil. We can say with confidence that these organic molecules came from the individual animals whose remains we tested."

The molecules appear to be aromatic compounds called quinones, which are found in modern crinoids and other animals. Quinones sometimes function as pigments or as toxins to discourage predators.

Chemostratigraphy indicates a relatively complete Late Permian to Early Triassic sequence in the western United States

Authors:

1. Matthew R. Saltzman (a)

2. Alexa R.C. Sedlacek (a)

Affiliations:

a. School of Earth Sciences, The Ohio State University, Columbus, Ohio 43210, USA

Abstract:

Although the latest Permian mass extinction and associated δ13C excursion are well documented from the Tethys Ocean, carbonate rocks preserving these events in the eastern Panthalassic Ocean (western Pangea) are unknown. We present δ13Ccarb from the Gerster and Thaynes (Permian and Triassic) Formations in the western United States and document a negative excursion with no evidence for major breaks in continuity. To further constrain the age of the δ13Ccarb excursion in the absence of index fossils, we analyzed the same samples for 87Sr/86Sr. When examining our new carbon and Sr data in the context of biostratigraphy and sequence stratigraphy, we conclude that parts of the western United States may preserve carbonate successions that span the latest Permian extinction.

a. Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742

b. Centre for Microscopy and Microanalysis, University of Western Australia, Perth, WA 6009, Australia

c. School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom

d. Department of Geological and Environmental Sciences, Faculty of Natural Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel

e. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, United Kingdom

f. School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom

Abstract:

It is generally thought that the sulfate reduction metabolism is ancient and would have been established well before the Neoarchean. It is puzzling, therefore, that the sulfur isotope record of the Neoarchean is characterized by a signal of atmospheric mass-independent chemistry rather than a strong overprint by sulfate reducers. Here, we present a study of the four sulfur isotopes obtained using secondary ion MS that seeks to reconcile a number of features seen in the Neoarchean sulfur isotope record. We suggest that Neoarchean ocean basins had two coexisting, significantly sized sulfur pools and that the pathways forming pyrite precursors played an important role in establishing how the isotopic characteristics of each of these pools was transferred to the sedimentary rock record. One of these pools is suggested to be a soluble (sulfate) pool, and the other pool (atmospherically derived elemental sulfur) is suggested to be largely insoluble and unreactive until it reacts with hydrogen sulfide. We suggest that the relative contributions of these pools to the formation of pyrite depend on both the accumulation of the insoluble pool and the rate of sulfide production in the pyrite-forming environments. We also suggest that the existence of a significant nonsulfate pool of reactive sulfur has masked isotopic evidence for the widespread activity of sulfate reducers in the rock record.

e. GeoQuEST Research Centre, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, Australia

Abstract:

The carpals from the Homo floresiensis type specimen (LB1) lack features that compose the shared, derived complex of the radial side of the wrist in Neandertals and modern humans. This paper comprises a description and three-dimensional morphometric analysis of new carpals from at least one other individual at Liang Bua attributed to H. floresiensis: a right capitate and two hamates. The new capitate is smaller than that of LB1 but is nearly identical in morphology. As with capitates from extant apes, species of Australopithecus, and LB1, the newly described capitate displays a deeply-excavated nonarticular area along its radial aspect, a scaphoid facet that extends into a J-hook articulation on the neck, and a more radially-oriented second metacarpal facet; it also lacks an enlarged palmarly-positioned trapezoid facet. Because there is no accommodation for the derived, palmarly blocky trapezoid that characterizes Homo sapiens and Neandertals, this individual most likely had a plesiomorphically wedge-shaped trapezoid (like LB1). Morphometric analyses confirm the close similarity of the new capitate and that of LB1, and are consistent with previous findings of an overall primitive articular geometry. In general, hamate morphology is more conserved across hominins, and the H. floresiensis specimens fall at the far edge of the range of variation for H. sapiens in a number of metrics. However, the hamate of H. floresiensis is exceptionally small and exhibits a relatively long, stout hamulus lacking the oval-shaped cross-section characteristic of human and Neandertal hamuli (variably present in australopiths). Documentation of a second individual with primitive carpal anatomy from Liang Bua, along with further analysis of trapezoid scaling relative to the capitate in LB1, refutes claims that the wrist of the type specimen represents a modern human with pathology. In total, the carpal anatomy of H. floresiensis supports the hypothesis that the lineage leading to the evolution of this species originated prior to the cladogenetic event that gave rise to modern humans and Neandertals.

That's a stock picture of the mountain in question. It just strengthens the prevailing wisdom that the Qaher 313 is a joke.

One of the pix of the Bird of Prey when they were first released was a fake, to be fair, showing it flying in Nevada in daylight. However, the BoP came from a credible source whereas the Qaher 313 is from one noted for faking.

Tuesday, February 12, 2013

Simon Fraser University evolutionary biologists Bruce Archibald and Rolf Mathewes, and Brandon University biologist David Greenwood, have discovered that modern tropical mountains' diversity patterns extended up into Canada about 50 million years ago.

Their findings confirm an influential theory about change in modern species diversity across mountains, and provide evidence that global biodiversity was greater in ancient times than now.

The scientific journal Palaeogeography, Palaeoclimatology, Palaeoecology has published their research.

About 45 years ago, an evolutionary biologist at the University of Pennsylvania theorized that change in species from site to site across mountain ranges in the tropics should be greater than in temperate latitudes.

Daniel Janzen reasoned that the great difference between summer and winter in temperate latitudes (high seasonality) offers a wide window to migrate across mountainous regions. The small difference in the tropics (low seasonality) allows a very narrow opportunity, annually. Consequently, communities across tropical mountains should have fewer of the same species. Many studies examining modern communities support this theory.

Archibald, Mathewes and Greenwood realized that fossil beds across a thousand kilometres of the ancient mountains of British Columbia and Washington provided a unique lens through which to deepen evaluation of this theory. Fifty million years ago, when these fossil beds were laid down, the world had low seasonality outside of the tropics, right to the poles. Because of this, if Janzen's theory is right, the pattern of biodiversity that he described in modern tropical mountains should have extended well into higher latitudes.

"We found that insect species changed greatly across British Columbia's and Washington State's ancient mountain ranges, like in the modern tropics," Archibald says, "exactly as Janzen's seasonality hypothesis predicted.

This implies that it's the particular seasonality now found in the modern tropics, not where that climate is situated globally, that affects this biodiversity pattern." He adds: "Sometimes it helps to look to the ancient past to better understand how things work today." The findings also bolster the idea that ancient Earth was a much more diverse world than now with many more species.

Having just completed the tortuous 48-hour journey from the South Pole to the US west coast, John Priscu is suffering from more than his fair share of jet lag. But his tiredness can't mask the excitement in his voice. After weeks of intense field work in Antarctica, he and his team have become the first to find life in a lake trapped under the frozen continent's ice sheet.

“Lake Whillans definitely harbours life,” he says. “It appears that there lies a large wetland ecosystem under Antarctica’s ice sheet, with an active microbiology.”

The lake in question is a 60-square-kilometre body of water that sits on the edge of the Ross Ice shelf in West Antarctica. To reach it, Priscu, a glaciologist at Montana State University in Bozeman, and his team had to drill down 800 metres of ice.

They arrived at their goal on 28 January, when their environmentally clean hot-water drill broke through to the lake's surface. What they found was a body of water just 2 metres or so deep — much shallower than the 10–25 metres seismic surveys had suggested, although Priscu notes that the lake may well have deeper spots.

The team put a camera down the borehole to make sure that the borehole was wide enough for sampling instruments to be deployed and returned safely. It was, and over the next few days, the scientists collected some 30 litres of liquid lake water and eight sediment cores from the lake’s bottom, each 60 centimetres long.

What precious stuff they had retrieved soon became clear under the on-site microscope. Both water and sediment contained an array of microbes that did not need sunlight to survive. The scientists counted about 1,000 bacteria per millilitre of lake water — roughly one-tenth the abundance of microbes in the oceans. In Petri dishes, the bacteria show a “really good growth rate”, says Priscu.

There is definitely hope for Europa. I have to wonder about Lake Vostok though.

The accretion of the Indian subcontinent to Eurasia triggered a massive faunal and floral exchange, with Gondwanan taxa entering into Asia and vice versa. The traditional view on the Indian–Asian collision assumes contact of the continental plates during the Early Eocene. Many biogeographic studies rely on this assumption. However, the exact mode and timing of this geological event is still under debate. Here we address, based on an extensive phylogenetic analysis of rhacophorid tree frogs, if there was already a Paleogene biogeographic link between Southeast Asia and India; in which direction faunal exchange occurred between India and Eurasia within the Rhacophoridae; and if the timing of the faunal exchange correlates with one of the recently suggested geological models. Rhacophorid tree frogs showed an early dispersal from India to Asia between 46 and 57 Ma, as reconstructed from the fossil record. During the Middle Eocene, however, faunal exchange ceased, followed by increase of rhacophorid dispersal events between Asia and the Indian subcontinent during the Oligocene that continued until the Middle Miocene. This corroborates recent geological models that argue for a much later final collision between the continental plates. We predict that the Oligocene faunal exchange between the Indian subcontinent and Asia, as shown here for rhacophorid frogs, also applies for other nonvolant organisms with an Indian–Asian distribution, and suggest that previous studies that deal with this faunal interchange should be carefully reinvestigated.

Monday, February 11, 2013

A team of UCLA-led researchers has identified a protein with broad virus-fighting properties that potentially could be used as a weapon against deadly human pathogenic viruses such as HIV, Ebola, Rift Valley Fever, Nipah and others designated "priority pathogens" for national biosecurity purposes by the National Institute of Allergy and Infectious Disease.

In a study published in the January issue of the journal Immunity, the researchers describe the novel antiviral property of the protein, cholesterol-25-hydroxylase (CH25H), an enzyme that converts cholesterol to an oxysterol called 25-hydroxycholesterol (25HC), which can permeate a cell's wall and block a virus from getting in.

Interestingly, the CH25H enzyme is activated by interferon, an essential antiviral cell-signaling protein produced in the body, said lead author Su-Yang Liu, a student in the department of microbiology, immunology and molecular genetics at the David Geffen School of Medicine at UCLA.

"Antiviral genes have been hard to apply for therapeutic purposes because it is difficult to express genes in cells," said Liu, who performed the study with principal investigator Genhong Cheng, a professor of microbiology, immunology and molecular genetics. "CH25H, however, produces a natural, soluble oxysterol that can be synthesized and administered.

"Also, our initial studies showing that 25HC can inhibit HIV growth in vivo should prompt further study into membrane-modifying cholesterols that inhibit viruses," he added.

The discovery is particularly relevant to efforts to develop broad-spectrum antivirals against an increasing number of merging viral pathogens, Liu said.

Working with Jerome Zack, a professor of microbiology, immunology and molecular genetics and an associate director of the UCLA AIDS Institute, the researchers initially found that 25HC dramatically inhibited HIV in cell cultures. Next, they administered 25HC in mice implanted with human tissues and found that it significantly reduced their HIV load within seven days. The 25HC also reversed the T-cell depletion caused by HIV.

Volcanoes are well known for cooling the climate. But just how much and when has been a bone of contention among historians, glaciologists and archeologists. Now a team of atmosphere chemists, from the Tokyo Institute of Technology and the University of Copenhagen, has come up with a way to say for sure which historic episodes of global cooling were caused by volcanic eruptions.

The answer lies in patterns of isotopes found in ancient volcanic sulfur trapped in ice core, patterns due to stratospheric photochemistry. Their mechanism is published in the highly recognized journal PNAS.

Better history through atmospheric chemistry

Matthew Johnson is an associate professor at the Department of Chemistry, University of Copenhagen where he studies chemical mechanisms in the atmosphere. He is thrilled at the prospect of giving a more precise tool to historians studying cold spells.

"Historical records are not always so accurate. Some may have been written down long after the fact, or when a different calendar was in use by a different culture. But the chemistry does not lie", says Johnson.

Method reads height by analyzing effect of sunshine

Powerful volcanoes can shoot gases through the atmosphere and high into the stratosphere where it can affect climate globally for a year or more. Less powerful eruptions can also have powerful impacts, but only locally, and for shorter times. And here's the trick. High plumes spend longer in the harsh sunlight of the stratosphere, and that changes the chemical signature of the sulfur in the plume. The balance of various isotopes is changed according to very precise rules, explains Mathew Johnson.

"Using our method we can determine whether a given eruption was powerful enough for the plume to enter the stratosphere affecting global climate. If we can find material from ancient eruptions it can now be used to give an accurate record of global volcanic events extending many hundreds of thousands of years back in time.", says Johnson.

Clue to fires found in ice

Strangely, the best place to look for traces of the fiery events is in ice. Tracking climate history is performed on cores drilled from the ice shields of Greenland and Antarctica. Much like tree rings, the snows of each year is compacted into a layer representing that year. As you go further down in the borehole, you descend into deeper history.

If volcanic material shows up in a layer, you know there was an eruption in that year. Using the method developed by Johnson and his colleagues it is now possible to analyze exactly how powerful a given eruption was.

"With the sulfur isotope method, we now have a way to prove whether a given eruption was so explosive that it entered the stratosphere, affecting global climate and civilizations, or, whether a given eruption was confined to the troposphere and local in its effects" says Johnson and goes on: "There are many controversial eruptions. The Mediterranean island of Santorini blew apart and caused the end of the Minoan culture. But there is a huge debate about when exactly this occurred. 1601 was the 'year without a summer' - but nobody knows where the volcano was that erupted. There's debate over whether there was an eruption on Iceland in 527, or 535, or 541. The sulfur isotope trick is a definite method to solve debates like this and get the most information out of the ice core records" Says Matthew Johnson.

Ultraviolet vision evolved at least eight times in birds from a common violet sensitive ancestor finds a study published in BioMed Central's open access journal BMC Evolutionary Biology. All of these are due to single nucleotide changes in the DNA.

Modern daytime birds either have violet sensitive or ultraviolet sensitive vision. Being ultraviolet sensitive alters visual cues used to select a mate, avoiding predators, and in finding food. Researchers from Uppsala University and the Swedish University of Agricultural Sciences sequenced the genes responsible for producing the light sensitive pigment (SWS1 opsin) from 40 species of birds, in 29 families.

Generating a phylogenetic tree from these sequences shows that there have been at least 14 shifts between violet and ultraviolet sensitive colour vision and back. An ancestor of Passeriformes (perching birds including larks, swallows, blackbirds, finches, birds of paradise, and crows) and Psittaciformes (parrots and allies) changed from the ancestral violet sensitive colour vision to ultraviolet and, in some cases passerines have reverted back to violet vision.

Anders Ödeen and Olle Håstad, who performed this research commented, "There are two different amino acid alterations that can each change bird colour vision from violet to ultraviolet. One particular single nucleotide change has occurred at least 11 separate times. In general during evolution once a colour shift has occurred all species from this ancestor keep it meaning that the rest of the eye and physiology, must also evolved to 'cement' in the new colour sensitivity."

Thursday, February 07, 2013

The demise of the dinosaurs is the world's ultimate whodunit. Was it a comet or asteroid impact? Volcanic eruptions? Climate change?

In an attempt to resolve the issue, scientists at the Berkeley Geochronology Center (BGC), the University of California, Berkeley, and universities in the Netherlands and the United Kingdom have now determined the most precise dates yet for the dinosaur extinction 66 million years ago and for the well-known impact that occurred around the same time.

The dates are so close, the researchers say, that they now believe the comet or asteroid, if not wholly responsible for the global extinction, at least dealt the dinosaurs their death blow.

"The impact was clearly the final straw that pushed Earth past the tipping point," said Paul Renne, BGC director and UC Berkeley professor in residence of earth and planetary science. "We have shown that these events are synchronous to within a gnat's eyebrow, and therefore the impact clearly played a major role in extinctions, but it probably wasn't just the impact."

The revised dates clear up lingering confusion over whether the impact actually occurred before or after the extinction, which was characterized by the almost overnight disappearance from the fossil record of land-based dinosaurs and many ocean creatures. The new date for the impact – 66,038,000 years ago – is the same within error limits as the date of the extinction, said Renne, making the events simultaneous.

He and his colleagues will report their findings in the Feb. 8 issue of the journal Science.

The extinction of the dinosaurs was first linked to a comet or asteroid impact in 1980 by the late UC Berkeley Nobel Laureate Luis Alvarez and his son, Walter, who is a UC Berkeley professor emeritus of earth and planetary science. A 110-mile-wide crater in the Caribbean off the Yucatan coast of Mexico is presumed to be the result of that impact. Called Chicxulub (cheek'-she-loob), the crater is thought to have been excavated by an object six miles across that threw into the atmosphere debris still found around the globe as glassy spheres or tektites, shocked quartz and a layer of iridium-enriched dust.

Renne decided last year to re-date the dinosaur extinction, which occurred at the boundary between the Cretaceous and Tertiary periods – the KT boundary – after recalibrating the 20-year-old accepted date and discovering that it now occurred 180,000 years BEFORE the impact. That earlier date was obtained in 1993 by BGC researchers using the same argon-argon method, which relies on the decay rate of a radioactive isotope of potassium.

"Everybody had always looked at the age for the KT boundary and compared it with the ages that we had gotten for the tektites and the melt rock from the Chicxulub crater and said, 'Ooh yeah, this is pretty much the same age,'" Renne said. "But they are not. They differ by 180,000 years, actually. So, from simply this esoteric calibration issue, I started to realize, 'Wow, there is a real problem here.'"

"Accurately dating the major Cretaceous-Paleogene extinction, including that of the dinosaurs, has been controversial," says H. Richard Lane, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

Renne and his BGC colleagues dated tektites from Haiti, analyzing them using a recalibrated argon-argon technique to determine how long ago the impact occurred. The tektite results agreed with recalibrated previous data but were more precise. They did the same for altered volcanic ash collected from the Hell Creek Formation in Montana, the source of many dinosaur fossils and one of the best sites to study the change in fossils from before and after the extinction.

A new Rice University-led study finds the real estate mantra "location, location, location" may also explain one of Earth's enduring climate mysteries. The study suggests that Earth's repeated flip-flopping between greenhouse and icehouse states over the past 500 million years may have been driven by the episodic flare-up of volcanoes at key locations where enormous amounts of carbon dioxide are poised for release into the atmosphere.

"We found that Earth's continents serve as enormous 'carbonate capacitors,'" said Rice's Cin-Ty Lee, the lead author of the study in this month's GeoSphere. "Continents store massive amounts of carbon dioxide in sedimentary carbonates like limestone and marble, and it appears that these reservoirs are tapped from time to time by volcanoes, which release large amounts of carbon dioxide into the atmosphere."

Lee said as much as 44 percent of carbonates by weight is carbon dioxide. Under most circumstances that carbon stays locked inside Earth's rigid continental crust.

"One process that can release carbon dioxide from these carbonates is interaction with magma," he said. "But that rarely happens on Earth today because most volcanoes are located on island arcs, tectonic plate boundaries that don't contain continental crust."

Earth's climate continually cycles between greenhouse and icehouse states, which each last on timescales of 10 million to 100 million years. Icehouse states -- like the one Earth has been in for the past 50 million years -- are marked by ice at the poles and periods of glacial activity. By contrast, the warmer greenhouse states are marked by increased carbon dioxide in the atmosphere and by an ice-free surface, even at the poles. The last greenhouse period lasted about 50 million to 70 million years and spanned the late Cretaceous, when dinosaurs roamed, and the early Paleogene, when mammals began to diversify.

Lee and colleagues found that the planet's greenhouse-icehouse oscillations are a natural consequence of plate tectonics. The research showed that tectonic activity drives an episodic flare-up of volcanoes along continental arcs, particularly during periods when oceans are forming and continents are breaking apart. The continental arc volcanoes that arise during these periods are located on the edges of continents, and the magma that rises through the volcanoes releases enormous quantities of carbon dioxide as it passes through layers of carbonates in the continental crust.

[...]

Lee said the study breaks with conventional theories about greenhouse and icehouse periods.

"The standard view of the greenhouse state is that you draw carbon dioxide from the deep Earth interior by a combination of more activity along the mid-ocean ridges -- where tectonic plates spread -- and massive breakouts of lava called 'large igneous provinces,'" Lee said. "Though both of these would produce more carbon dioxide, it is not clear if these processes alone could sustain the atmospheric carbon dioxide that we find in the fossil record during past greenhouses."

[...]

Lee developed the idea that continental-arc volcanoes could pump carbon dioxide into the atmosphere. One indicator was evidence from Mount Etna in Sicily, one of the few active continental-arc volcanoes in the world today. Etna produces large amounts of carbon dioxide, Lee said, so much that it is often considered an outlier in global averages of modern volcanic carbon dioxide production.

Tectonic and petrological evidence indicated that many Etna-like volcanoes existed during the Cretaceous greenhouse, Lee said. He and colleagues traced the likely areas of occurrence by looking for tungsten-rich minerals like scheelite, which are formed on the margins of volcanic magma chambers when magma reacts with carbonates. It wasn't easy; Lee spent an entire year pouring through World War II mining surveys from the western U.S. and Canada, for example.

"There is evidence to support our idea, both in the geological record and in geophysical models, the latter of which show plausibility," he said. For example, in a companion paper published last year in G-Cubed, Lenardic used numerical models that showed the opening and breakup of continents could change the nature of subduction zones, generating oscillations between continental- and island-arc dominated states.

Though the idea in the GeoSpheres study is still a theory, Lee said, it has some advantages over more established theories because it can explain how the same basic set of geophysical conditions could produce and sustain a greenhouse or an icehouse for many millions of years.

"The length of subduction zones and the number of arc volcanoes globally don't have to change," Lee said. "But the nature of the arcs themselves, whether they are continental or oceanic, does change. It is in the continental-arc stage that CO2 is released from an ever-growing reservoir of carbonates within the continents."